‘He [Carter] would be a huge loss. But injuries are one of those things.’

Former All Blacks captain Taine Randell said Carter’s loss would have a massive impact on the side’s chances of success.

‘For us, he is crucial … Carter is probably the most important guy,’ Randell said.

‘I would still back the All Blacks but certainly not with the same confidence.’

Carter tore a groin muscle during a kicking drill at the captain’s run in preparation for Sunday’s match against Canada. Carter had just been named All Blacks captain for the first time in his career after Test centurion Richie McCaw withdrew because of ongoing problems to the foot injury that has hampered his season and tournament.

Both Nathan and Randell told Rugbyheaven they had concerns about Carter’s back-up, Canterbury’s Colin Slade.

Nathan said: ‘I’m not that much of a fan for Slade.

‘I would maybe even change [Piri] Weepu into first five. The drop in level to how Colin Slade operates is so big,’ said Randell. ‘That is why he [Carter] is so important to us.’

Slade was shocking in the 18-5 defeat against the Boks in Port Elizabeth and struggled as the starting option in the 83-8 win against Japan a fortnight ago. Cruden was the form flyhalf in the domestic ITM Cup, but his Test debut against the Wallabies in Sydney last year was not as flash.

Henry appeared to groom Cruden, then just 20, as Carter’s understudy in 2010 with performances against Wales and Australia, but did not take him on the end of year tour, preferring to play Stephen Donald. This proved disastrous. In 2011 Slade, despite limited Super Rugby game time because of injury, was the go to man.

The best option outside of Carter is London-based Nick Evans, but the New Zealand Rugby Union policy is no player will be selected for the All Blacks unless he is playing out of New Zealand. This rules out Evans as it did tighthead Carl Hayman, who plays for Toulon.

Carter’s withdrawal from the tournament has narrowed the odds on a New Zealand victory and improved the price on one of South Africa or Australia winning the tournament.